I think they both look great, however, I would go with the first one. It looks more "Spring"y and I think if you have to take picture afterwards you will be the one that everyone notices. It's your graduation, so all eyes should be on you!

I'm still in the middle of my weight loss, I'd like to lose around 15 more pounds, but I always appreciate looking at everyone else's pictures, and I also think posting pictures I never wanted anyone in the world to see will help motivate me more. The first two are from when I weighed about 180, and the last two were taken today.
180... notice my chins and bra fat. Nice Ashley, nice. I cried when I saw this one for the first time.

I'm on the left, the other two are my mom and my stinkin skinny little sister who motivates me to lose weight every time I see her shoulder bones sticking out. Just kidding, I love her.

Boyfriend and I, Nov 2009. I was about 165ish. It was cold out and I felt terrible about myself so I was wearing as much as possible to cover myself up, which just made me feel even bigger.

Boyfriend again, about 154 taken a few weeks ago. We make very serious faces. Yes, I'm pale.

That's my butt today. I didn't ever take a before picture of it because they don't make wide angle lenses for cell phone cameras.